7.3 Broadcast mode 5G ProSe direct communication over PC5

24.5543GPPProximity-services (ProSe) in 5G System (5GS) protocol aspectsRelease 17Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

7.3.1 Overview

This clause describes the 5G ProSe communication over PC5 reference point in broadcast mode operation. The UE is configured with the related information as described in clause 5.2.4.

7.3.2 Transmission of broadcast mode 5G ProSe communication over PC5

7.3.2.1 Initiation

7.3.2.1.1 Broadcast mode 5G ProSe communication over PC5 triggered by upper layers

When the UE is requested by upper layers to send data unit(s) of a ProSe application identified by a ProSe identifier using 5G ProSe communication over PC5, the request from the upper layers includes:

a) the data unit(s) of the ProSe application;

b) the ProSe identifier of the ProSe application for the data unit(s);

c) the type of data in the data unit(s) (i.e., IP, Ethernet, Address Resolution Protocol, or Unstructured);

d) optionally the communication mode which is set to broadcast mode; and

e) optionally the 5G ProSe application requirements (e.g., priority requirement, reliability requirement, delay requirement).

Upon a request from upper layers to send data unit(s) of a ProSe application identified by a ProSe identifier using 5G ProSe communication over PC5, if:

a) the UE is configured with ProSe identifier to ProSe NR frequency mapping rules for 5G ProSe communication over PC5 as specified in clause 5.2.4; and

b) there are one or more ProSe NR frequencies associated with the ProSe identifier of the ProSe application for the data unit(s) in the current geographical area,

then the UE passes the one or more ProSe NR frequencies associated with the ProSe identifier of the ProSe application and the communication mode which is set to broadcast mode for the data unit(s) to the lower layers.

Upon a request from upper layers to send data unit(s) of a ProSe application identified by a ProSe identifier using 5G ProSe communication over PC5, the UE determines the NR Tx profiles based on the list of ProSe identifiers to NR Tx profiles for broadcast and groupcast mapping rules as specified in clause 5.2.4 and passes the NR Tx profiles to the lower layers as specified in clause 7.3.2.2. Additionally, when the UE is not served by NG-RAN, the UE also passes the configured PC5 DRX configuration as specified in clause 5.2.4 to the lower layers.

The UE shall maintain a list of ProSe services the UE is interested in, including the ProSe services in use, the ProSe services that the UE is interested for transmission or both, for each destination layer-2 ID. The ProSe services are identified by the ProSe identifiers.

NOTE: How the UE maintains the list of ProSe services the UE is interested in is left to UE implementation.

Then, if:

a) the following conditions are met:

1) the UE is served by NG-RAN for 5G ProSe communication;

2) the UE intends to use the radio resources (i.e., carrier frequency) provided by a serving cell;

3) the registered PLMN is in the list of PLMNs in which the UE is authorized to use 5G ProSe communication over PC5 when the UE is served by NG-RAN for 5G ProSe communication over PC5 as specified in clause 5.2.4; and

4) the ProSe identifier of the ProSe application is included in the list of ProSe applications authorized for 5G ProSe communication over PC5 as specified in clause 5.2.4; or

b) the following conditions are met:

1) the UE is:

i) not served by NG-RAN for 5G ProSe communication over PC5;

ii) in limited service state as specified in 3GPP TS 23.122 [14], if the reason for the UE being in limited service state is one of the following:

A) the UE is unable to find a suitable cell in the selected PLMN as specified in 3GPP TS 38.304 [15];

B) the UE received a REGISTRATION REJECT message or a SERVICE REJECT message with the 5GMM cause #11 "PLMN not allowed" as specified in 3GPP TS 24.501 [11]; or

C) the UE received a REGISTRATION REJECT message or a SERVICE REJECT message with the 5GMM cause #7 "5GS services not allowed" as specified in 3GPP TS 24.501 [11]; or

iii) in limited service state as specified in 3GPP TS 23.122 [14] for reasons other than A), B) or C) above and located in a geographical area for which the UE is provisioned with "non-operator managed" radio parameters as specified in clause 5.2.4;

2) the UE is authorized to use 5G ProSe communication over PC5 when the UE is not served by NG-RAN for 5G ProSe communication as specified in clause 5.2.4; and

3) the ProSe identifier of the ProSe application is included in the list of ProSe applications authorized for 5G ProSe communication over PC5 as specified in clause 5.2.4;

then the UE shall proceed as specified in clause 7.3.2.1.2, else the UE shall not perform transmission of 5G ProSe communication over PC5.

7.3.2.1.2 PC5 QoS flow match and establishment

In order to determine if any existing PC5 QoS flow matches the request from upper layers, UE shall proceed as follows:

a) according to the PC5 QoS mapping rules specified in clause 5.2.4, the UE shall use the PC5 QoS parameters corresponding to the ProSe identifier and optionally 5G ProSe application requirements;

b) according to the ProSe identifier to destination layer-2 ID for broadcast mapping rules specified in clause 5.2.4, the UE shall use the destination layer-2 ID corresponding to the ProSe identifier;

c) if there is no existing context for the destination layer-2 ID, then:

1) build a new context for the destination layer-2 ID;

2) self-assign a new source layer-2 ID; and

NOTE: The UE implementation ensures that the value of the self-assigned source layer-2 ID is different from any other self-assigned source layer-2 ID(s) in use for 5G ProSe direct discovery as specified in clause 6.2.14, clause 6.2.15 and clause 8.2.1 and is different from any other provisioned destination layer-2 ID(s) as specified in clause 5.2.

3) pass the source layer-2 ID and the destination layer-2 ID to lower layers.

d) if in the context for the destination layer-2 ID, there is no PC5 QoS rule for the existing PC5 QoS flow(s) matching the service data or request, the UE shall derive the PC5 QoS parameters based on the 5G ProSe application requirements provided by the upper layers (if available) and the ProSe identifier according to the PC5 QoS mapping rules defined in clause 5.2.4 and shall perform the following:

1) if there is no existing PC5 QoS flow that fulfils the derived PC5 QoS parameters, then the UE shall create a new PC5 QoS flow by performing the following operations:

i) self-assign a new PQFI;

ii) create a new PC5 QoS flow context which contains:

A) the PQFI;

B) the ProSe identifier(s); and

C) the derived PC5 QoS parameters;

iii) create a new PC5 QoS rule which contains:

A) a PC5 QoS rule identifier;

B) the PQFI;

C) a set of packet filters; and

D) a precedence value; and

iv) pass the following parameters to the lower layers:

A) the PQFI;

B) the PC5 QoS parameters;

C) the source layer-2 ID and the destination layer-2 ID; and

D) the NR Tx profile, if available, as determined for the respective ProSe identifier based on the list of ProSe identifiers to NR Tx profiles for broadcast and groupcast mapping rules as specified in clause 5.2.4;

2) if there is an existing PC5 QoS flow that fulfils the derived PC5 QoS parameters, then the UE shall update the PC5 packet filter set in the PC5 QoS rule of this PC5 QoS flow, e.g. add the new packet filter in the PC5 QoS rule of this existing PC5 QoS flow; and

3) the UE shall use the new PC5 QoS flow created as described in bullet 1) or the existing PC5 QoS flow with the updated PC5 QoS rules as described in bullet 2) to perform the transmission of 5G ProSe communication over PC5 as specified in clause 7.3.2.2; and

e) if in the context for the destination layer-2 ID, there is a PC5 QoS rule for the existing PC5 QoS flow matching the service data or request, the UE shall use this existing PC5 QoS flow to perform transmission of 5G ProSe communication over PC5 as specified in clause 7.3.2.2.

Three types of packet filters are supported for broadcast mode 5G ProSe direct communication over PC5, i.e., the ProSe IP packet filter set, the ProSe packet filter set and the ProSe Ethernet packet filter set. The three types of packet filters are defined the same as specified in clause 7.2.7.

7.3.2.2 Transmission

The UE shall include the data unit(s) in a protocol data unit with the following parameters:

a) a layer-3 protocol data unit type (see 3GPP TS 38.323 [16]) set to:

1) IP, if the data unit(s) contains IP data;

2) Ethernet, if the data unit(s) contains Ethernet data;

3) Address Resolution Protocol, if the data unit(s) contains Address Resolution Protocol data; or

4) Unstructured, if the data unit(s) contains Unstructured data;

b) the source layer-2 ID set to the layer-2 ID self-assigned by the UE for 5G ProSe communication over PC5 as specified in clause 7.3.2.1.2;

c) the destination layer-2 ID set to the destination layer-2 ID associated with the ProSe identifier of the ProSe application in this list of ProSe applications authorized for 5G ProSe communication over PC5 as specified in clause 5.2.4;

d) if the data unit(s) contains IP data, the source IP address set to the source IP address allocated to the UE as specified in clause 7.3.4;

NOTE: How to set the destination IP address is left to UE implementation.

e) the PQFI set to the value corresponding to the PC5 QoS rules as specified in clause 7.3.2.1, and

f) if the UE is configured with ProSe identifiers to NR Tx profiles for broadcast and groupcast mapping rules for 5G ProSe direct communication over PC5 as specified in clause 5.2.4, the NR Tx profile associated with the ProSe identifier as specified in clause 5.2.4. If the list of ProSe services the UE is interested in for the destination layer-2 ID changes, the UE shall provide all the NR Tx profiles for the ProSe identifier(s) in the list of ProSe services the UE is interested in for the destination layer-2 ID to the lower layers,

then UE shall request radio resources for 5G ProSe communication over PC5 as specified in 3GPP TS 38.300 [21] and pass the data unit(s) on the PC5 QoS Flow identified by the PQFI to lower layers for transmission. The PC5 QoS Rules corresponding to the PQFIs map the data unit(s) with the same ProSe identifier and with the same PC5 QoS parameters to the same PC5 QoS Flow and apply PQFI to the data unit(s).

If the UE is camped on a serving cell indicating that 5G ProSe communication over PC5 is supported by the network, but not broadcasting any carrier frequencies and radio resources for 5G ProSe communication over PC5 as specified in 3GPP TS 38.331 [13], the UE shall request radio resources for 5G ProSe communication over PC5 as specified in 3GPP TS 24.501 [11].

7.3.2.3 Procedure for UE to use provisioned radio resources for 5G ProSe communication over PC5

When the UE is not served by NG-RAN for 5G ProSe communication and is authorized to use 5G ProSe communication over PC5, the UE shall identify the NR-PC5 to be used for 5G ProSe communication over PC5. After identifying NR-PC5 to be used for 5G ProSe communication over PC5, the UE shall select the corresponding radio parameters to be used for 5G ProSe communication over PC5 as follows:

a) if the UE can determine itself located in a geographical area and the UE is provisioned with radio parameters for the geographical area, the UE shall select the radio parameters associated with that geographical area; or

b) in all other cases, the UE shall not initiate 5G ProSe communication over PC5.

If the UE intends to use "non-operator managed" radio parameters as specified in clause 5.2.4, the UE shall initiate 5G ProSe communication over PC5 with the selected radio parameters.

If the UE intends to use "operator managed" radio parameters as specified in clause 5.2.4, before initiating 5G ProSe communication over PC5, the UE shall check with lower layers whether the selected radio parameters can be used in the current location without causing interference to other cells as specified in 3GPP TS 38.331 [13]; and:

a) if the lower layers indicate that the usage would not cause any interference, the UE shall initiate 5G ProSe communication over PC5; or

NOTE: If the lower layers find that there exists a cell operating the provisioned radio resources (i.e., carrier frequency) and the cell belongs to the registered PLMN or a PLMN equivalent to the registered PLMN and the UE is authorized for 5G ProSe communication over PC5 in this PLMN, the UE can use the radio parameters indicated by the cell as specified in 3GPP TS 38.331 [13].

b) else if the lower layers report that one or more PLMNs operate in the provisioned radio resources (i.e., carrier frequency) then:

1) if the following conditions are met:

i) none of the PLMNs reported by the lower layers is the registered PLMN or equivalent to the registered PLMN;

ii) at least one of the PLMNs reported by the lower layers is in the list of authorized PLMNs for 5G ProSe communication over PC5 and provides radio resources for 5G ProSe communication over PC5 as specified in 3GPP TS 38.331 [13]; and

iii) the UE does not have an emergency PDU session;

then the UE shall:

i) if in 5GMM-IDLE mode, perform PLMN selection triggered by 5G ProSe communication over PC5 as specified in 3GPP TS 23.122 [14]; or

ii) else if in 5GMM-CONNECTED mode, either:

A) perform a De-registration procedure as specified in 3GPP TS 24.501 [11] and then perform PLMN selection triggered by 5G ProSe communication over PC5 as specified in 3GPP TS 23.122 [14]; or

B) not initiate 5G ProSe communication over PC5.

Whether the UE performs i) or ii) above is left up to UE implementation; or

2) else the UE shall not initiate 5G ProSe communication over PC5.

If the registration to the selected PLMN is successful, the UE shall proceed with the procedure to initiate 5G ProSe communication over PC5 as specified in clause 7.3.2.1.

If the UE is performing 5G ProSe communication over PC5 using radio parameters associated with a geographical area and moves out of that geographical area, the UE shall stop performing 5G ProSe communication over PC5 and then:

a) if the UE is not served by NG-RAN for 5G ProSe communication over PC5 or the UE intends to use radio resources for 5G ProSe communication over PC5 other than those operated by the serving cell, the UE shall select appropriate radio parameters for the new geographical area as specified above; or

b) if the UE is served by NG-RAN for 5G ProSe communication over PC5 and intends to use radio resources for 5G ProSe communication over PC5 operated by the serving cell, the UE shall proceed with the procedure to initiate 5G ProSe communication over PC5 when served by NG-RAN for 5G ProSe communication over PC5.

7.3.2.4 Privacy of 5G ProSe transmission over PC5

Upon initiating transmission of 5G ProSe communication over PC5, if:

a) the ProSe identifier of a ProSe application requesting transmission of 5G ProSe communication over PC5 is in the list of ProSe applications which require privacy for 5G ProSe communication over PC5 as specified in clause 5.2.4; and

b) the UE is located in a geographical area in which this ProSe application requires privacy for 5G ProSe communication over PC5 as specified in clause 5.2.4, or the UE is not provisioned any geographical areas in which this ProSe applications requires privacy for 5G ProSe communication over PC5,

then the UE shall proceed as follows:

a) if timer T5100 is not running, start timer T5100 and set its timer value as the privacy timer value as specified in clause 5.2.4;

b) upon:

1) getting an indication from upper layers that the application layer identifier has been changed; or

2) timer T5100 expiry,

then:

1) change the value of the source layer-2 ID self-assigned by the UE for the 5G ProSe communication over PC5;

NOTE 1: The UE implementation ensures that the value of the self-assigned source layer-2 ID is different from any other self-assigned source layer-2 ID(s) in use for 5G ProSe direct discovery as specified in clause 6.2.14, clause 6.2.15 and clause 8.2.1 and is different from any other provisioned destination layer-2 ID(s) as specified in clause 5.2.

2) if the data unit(s) contains IP data, change the value of the source IP address self-assigned by the UE for 5G ProSe communication over PC5;

NOTE 2: How to change and randomise the UE’s source layer-2 ID and source IP address including IP prefix (if used) is specified in clause 5.5 of 3GPP TS 33.536 [37] with the consideration of replacing V2X with 5G ProSe.

3) provide an indication to upper layers that the source layer-2 ID, or the source IP address, or both the source layer-2 ID and the source IP address are changed;

4) pass the changed source layer-2 ID and destination layer-2 ID, along with the corresponding PQFI down to the lower layer;

5) restart timer T5100; and

6) upon stopping transmission of the 5G ProSe communication over PC5, stop timer T5100.

7.3.3 Reception of broadcast mode 5G ProSe communication over PC5

The UE may be configured by upper layers with one or more destination layer-2 ID(s) for reception of data unit(s) over PC5.

The UE shall maintain a list of ProSe services the UE is interested in, including the ProSe services in use, ProSe services that the UE is interested for reception or both, for each destination layer-2 ID. The ProSe services are identified by the ProSe identifiers.

NOTE 1: How the UE maintains the list of ProSe services it is interested in is left to UE implementation.

The receiving UE shall determine the PC5 QoS parameters for this broadcast ProSe service in the same way described in clause 7.3.2.1.2 and shall determine the NR Tx profile as described in clause 5.2.4, and shall provide the PC5 QoS parameters, the NR Tx profile if available and the destination layer-2 ID(s) to lower layers. If the list of ProSe services the UE is interested in for the destination layer-2 ID changes, the receiving UE shall update the lower layers for the NR Tx Profiles information by providing all the NR Tx profiles for the ProSe identifier(s) in the list of ProSe services the UE is interested in for the destination layer-2 ID to the lower layers.

For each received protocol data unit over PC5, the receiving UE shall check if the destination layer-2 ID of the received protocol data unit matches one of the configured destination layer-2 IDs. If yes, the UE shall then check whether the protocol data unit type as defined 3GPP TS 38.323 [16] provided by the lower layers for the received packet is set to IP, Ethernet, Address Resolution Protocol or Unstructured and pass the protocol data unit to the corresponding upper layer entity.

NOTE 2: When the PC5 DRX operation is needed based on the provided NR Tx profile if any, the lower layers use PC5 QoS parameters and the destination layer-2 ID(s) to determine the PC5 DRX parameter values (see 3GPP TS 38.300 [21]) for reception operation over PC5 reference point.

7.3.4 IP address allocation for broadcast mode 5G ProSe communication over PC5

When the UE needs to perform 5G ProSe communication over PC5 reference point in broadcast mode operation and the type of data in the data unit is IP, the UE:

a) for IPv4,

1) shall use the pre-configured link local IPv4 address as source address; or

2) shall use dynamic configuration of IPv4 link-local addresses as specified in IETF RFC 3927 [38] if there is no pre-configured link local IPv4 address; and

b) for IPv6,

1) shall auto-configure a link local IPv6 address following procedures defined in IETF RFC 4862 [25]; and

2) may use this IP address for direct communication without sending Neighbour Solicitation and Neighbour Advertisement message for Duplicate Address Detection.